Oil Cooler and A/C Ballast Resistors - Success
08-05-2011, 02:33 PM
#1
Burning Brakes
Thread Starter
Oil Cooler and A/C Ballast Resistors - Success
Having convinced myself that the original ballast resistors controlling the fan low speed operation for both the oil cooler and A/C condenser were bad, I did a lot of research into the best way to replace them. The search function turned up a lot of posts on the topic, and most of them talked about what a PITA job it was to replace these parts. Then I ran into a posting that suggested removing the front bumper for access to both resistors.
My decision to remove the bumper was more to get into that area of the car for inspection and cleaning of the area. I guess it is a "curiosity thing" with me, just wanting to take things apart to see what is involved and to inspect things that you cannot without removing things.
Having taken that route, I am here to report that without a doubt.....removing the bumper is absolutely the easiest way to gain access to the resistors.
You can find the DIY for bumper removal in the PCA-Workshop accessible on this forum. Very well written instructions.
The single activity that takes the longest to perform is putting the front of the car up on jack stands. Took me about 30 minutes to jack the car up and place the jack stands correctly. That included the time to gather all the tools and hardware needed to put the car up in the air.
Once on jack stands, it takes about 30 minutes to remove all the screws, bolts, and nuts needed to remove the bumper. This included the time required to remove the front fender liners in both fender wells (which needs to be done anyway whether you elect to remove the bumper or not). Once the fender well liners are off, all the hardware that has to be removed to get the bumper off the car is within easy view and access and it took about 10 minutes to run around the edges of the bumper to find, remove, and bag/mark all the hardware. There is a single hold down metal strip located in the cars trunk that is attached with ( 6) screws.
I want to stress that none of the fasteners needing to be removed are difficult to get to or remove. Piece of cake.
You'll also need to remove the turn signal and fog lights which are also accessed easily from the exterior of the car. They need to come out simply so that you can disconnect their wiring harness plugs to allow the bumper to slip over the wiring as you pull it off the car.
There is also a drain line on each side that has to be slipped off its connector that passes through the bottom of the bumper.
With the bumper now free, use your hands to free it around its perimeter and then work the bumper off the car. This activity took me about 2 minutes to do. The bumper is all plastic and is light, so don't worry about being able to lift it. Removal is easily a one man job.
With the bumper off the car, you can now access the oil cooler and the condenser for replacement of the resistors. Unfortunately, you will need to drop both the oil cooler and the condenser to gain easy access to the resistors. But, that, too is an easy thing to do. For the oil cooler, you simply want to remove the "shelf" that the cooler sits on, which then allows the cooler to hang down on its hoses. The shelf is held to the body of the car with (3) nuts. You also have to free up a support strut and the upper rubber mount for the cooler. Both of these fasteners are 10 mm nuts that are right there.......takes seconds to remove them. With the shelf removed, the cooler can be left to hang down on its hoses.
Just above where the cooler was installed, you will now see the elongated aluminum heat sink that has the ballast resistor mounted to its top side. You will need to remove the heat sink with the resistor still attached. There are (3) small nuts that attach the heat sink to the inner fender of the car. Again, use a socket and a 12" extension to easily access the attachment nuts. You'll need to disconnect the electrical plug for the resistor in order to remove the heat sink/resistor from the car. All of this is easy. It's taking me longer to type this out than it took to actually do the work in the car!
Once the heat sink and resistor are out of the car, you can easily remove the nut that mounts the resistor to the heat sink. The new replacement resistor will come with an aluminum heat sink "plate" that needs to be mounted sandwiched between the new resistor and the old heat sink. Porsche did this since there is no way to know the condition of the old heat sink upon removal of the old resistor. In my case, there was a great deal of corrosion and dirt/mud in the area where the old resistor was mounted. Though the heat sink supplied with the new resistor is probably adequate to dissipate the heat, you can improve things by cleaning up the mating area on the old heat sink. Ideally, you would like to have the new heat sink sit on the old heat sink with 100% contact between the two parts. To achieve this use sandpaper, steel wool, or wire brushes to clean the area until all corrosion is removed and you are left with a shining aluminum surface where the two parts mate with one another.
With the new resistor bolted onto the old heat sink, assembly is simply the reverse of the above.
Actually, with removal of the A/C condenser attached to its "shelf" (exactly the same as for the oil cooler), changing the resistor out {which is bolted to the back side of the condenser housing) is much easier and faster than changing its sister resistor out on the oil cooler since there is no separate aluminum heat sink to remove, as was the case with the oil cooler.
With the condenser (attached to its shelf) broken loose from the inner fender, you can simply pull the shelf/condenser assembly out from the body of the car with one hand, while allowing it to hang on all its hoses, giving you unobstructed access with your other hand to the 4mm allen head cap screw that fastens the resistor to the back side of the condenser housing. So much access that I was able to use a 4mm allen head wrench at first to "break" the bolt loose (some minor corrosion had set in since the resistor was installed 13 years ago!). It was easy to get my entire hand in the area to use the wrench. Once I had broken the bolt loose, I switched to a 4mm allen head socket on a 3/8" drive socket wrench (would have been a little bit easier with a 1/4" drive, but my 3/8" gear was close at hand) which allowed me to quickly finish the unbolting operation.
Oddly, for my car anyway (a 1998 model), the oil cooler resistor was bolted to its heat sink with a hex head cap screw, while the A/C resistor was bolted to the housing with an allen head cap screw. The Germans never cease to amaze me! Being an engineer myself, I spend too much time trying to understand "why" they do the things they do!
The corrosion on the end of the cap screw that attached the resistor to the housing was due to its exposure to the atmosphere over the years. The cap screw is a bit long and the end of the screw protrudes about a 1/4" beyond the mating nut (which is welded to the inside of the condenser housing). So, over the 13 years of service, the "naked" end of the screw was in the cooling fan air stream and apparently exposed to water that entered the area while the car was being driven, causing it to corrode. I was in a hurry and simply cleaned up the corrosion by running the screw through a die; but, you might want to consider changing the screw out to stainless......just in case you need to ever again change out the resistor. One of the posters had mentioned that the screw was corroded into place and he ended up rounding off the allen head socket.
As with the re-assembly of the oil cooler side of the car, assembly is simply "the reverse of the disassembly steps".
One last note. Upon inspection of the "inlet" side to the condenser, I was surprised to find a compacted build up of straw, leaves, and other debris impeding air flow through the condenser. It's hard to imagine how all that debris found its way through the opening in the bumper, but obviously it did. Be sure and inspect your condenser for such obstructions. I was able to easily vacuum out the debris after breaking it up with a screw driver (it was really packed in there). I also used compressed air to blow through from the other side of the condenser (the outlet side) to blow out any loose debris that might have been packed around the cooling fins.
That's the job. In total, I probably actually spent about 3 hours to do the work, of which a lot was spent just getting my tools ready and jacking the car up and putting it on jack stands. Removal and replacement of the bumper took about an hour. As you would guess, re-fitting the bumper took a while longer since it is a bit cumbersome (but not heavy) and I was careful setting it in place.
I also took extra time to clean up the areas exposed that were pretty dirty from never having been accessed in 13 years. So, in retrospect, I would say that the entire job is a simple DIY chore that can easily be accomplished in a half day by the average wrencher. I worked at a leisurely pace which included the consumption of some adult beverages and spent about 4 hours in my garage.
Certainly, abandoning the original resistors in place, and relocating the replacement resistors would have been much easier as has been noted by other folks. But, for me, there is something that likes to keep things "stock". Just the way I am wired, I guess.
My decision to remove the bumper was more to get into that area of the car for inspection and cleaning of the area. I guess it is a "curiosity thing" with me, just wanting to take things apart to see what is involved and to inspect things that you cannot without removing things.
Having taken that route, I am here to report that without a doubt.....removing the bumper is absolutely the easiest way to gain access to the resistors.
You can find the DIY for bumper removal in the PCA-Workshop accessible on this forum. Very well written instructions.
The single activity that takes the longest to perform is putting the front of the car up on jack stands. Took me about 30 minutes to jack the car up and place the jack stands correctly. That included the time to gather all the tools and hardware needed to put the car up in the air.
Once on jack stands, it takes about 30 minutes to remove all the screws, bolts, and nuts needed to remove the bumper. This included the time required to remove the front fender liners in both fender wells (which needs to be done anyway whether you elect to remove the bumper or not). Once the fender well liners are off, all the hardware that has to be removed to get the bumper off the car is within easy view and access and it took about 10 minutes to run around the edges of the bumper to find, remove, and bag/mark all the hardware. There is a single hold down metal strip located in the cars trunk that is attached with ( 6) screws.
I want to stress that none of the fasteners needing to be removed are difficult to get to or remove. Piece of cake.
You'll also need to remove the turn signal and fog lights which are also accessed easily from the exterior of the car. They need to come out simply so that you can disconnect their wiring harness plugs to allow the bumper to slip over the wiring as you pull it off the car.
There is also a drain line on each side that has to be slipped off its connector that passes through the bottom of the bumper.
With the bumper now free, use your hands to free it around its perimeter and then work the bumper off the car. This activity took me about 2 minutes to do. The bumper is all plastic and is light, so don't worry about being able to lift it. Removal is easily a one man job.
With the bumper off the car, you can now access the oil cooler and the condenser for replacement of the resistors. Unfortunately, you will need to drop both the oil cooler and the condenser to gain easy access to the resistors. But, that, too is an easy thing to do. For the oil cooler, you simply want to remove the "shelf" that the cooler sits on, which then allows the cooler to hang down on its hoses. The shelf is held to the body of the car with (3) nuts. You also have to free up a support strut and the upper rubber mount for the cooler. Both of these fasteners are 10 mm nuts that are right there.......takes seconds to remove them. With the shelf removed, the cooler can be left to hang down on its hoses.
Just above where the cooler was installed, you will now see the elongated aluminum heat sink that has the ballast resistor mounted to its top side. You will need to remove the heat sink with the resistor still attached. There are (3) small nuts that attach the heat sink to the inner fender of the car. Again, use a socket and a 12" extension to easily access the attachment nuts. You'll need to disconnect the electrical plug for the resistor in order to remove the heat sink/resistor from the car. All of this is easy. It's taking me longer to type this out than it took to actually do the work in the car!
Once the heat sink and resistor are out of the car, you can easily remove the nut that mounts the resistor to the heat sink. The new replacement resistor will come with an aluminum heat sink "plate" that needs to be mounted sandwiched between the new resistor and the old heat sink. Porsche did this since there is no way to know the condition of the old heat sink upon removal of the old resistor. In my case, there was a great deal of corrosion and dirt/mud in the area where the old resistor was mounted. Though the heat sink supplied with the new resistor is probably adequate to dissipate the heat, you can improve things by cleaning up the mating area on the old heat sink. Ideally, you would like to have the new heat sink sit on the old heat sink with 100% contact between the two parts. To achieve this use sandpaper, steel wool, or wire brushes to clean the area until all corrosion is removed and you are left with a shining aluminum surface where the two parts mate with one another.
With the new resistor bolted onto the old heat sink, assembly is simply the reverse of the above.
Actually, with removal of the A/C condenser attached to its "shelf" (exactly the same as for the oil cooler), changing the resistor out {which is bolted to the back side of the condenser housing) is much easier and faster than changing its sister resistor out on the oil cooler since there is no separate aluminum heat sink to remove, as was the case with the oil cooler.
With the condenser (attached to its shelf) broken loose from the inner fender, you can simply pull the shelf/condenser assembly out from the body of the car with one hand, while allowing it to hang on all its hoses, giving you unobstructed access with your other hand to the 4mm allen head cap screw that fastens the resistor to the back side of the condenser housing. So much access that I was able to use a 4mm allen head wrench at first to "break" the bolt loose (some minor corrosion had set in since the resistor was installed 13 years ago!). It was easy to get my entire hand in the area to use the wrench. Once I had broken the bolt loose, I switched to a 4mm allen head socket on a 3/8" drive socket wrench (would have been a little bit easier with a 1/4" drive, but my 3/8" gear was close at hand) which allowed me to quickly finish the unbolting operation.
Oddly, for my car anyway (a 1998 model), the oil cooler resistor was bolted to its heat sink with a hex head cap screw, while the A/C resistor was bolted to the housing with an allen head cap screw. The Germans never cease to amaze me! Being an engineer myself, I spend too much time trying to understand "why" they do the things they do!
The corrosion on the end of the cap screw that attached the resistor to the housing was due to its exposure to the atmosphere over the years. The cap screw is a bit long and the end of the screw protrudes about a 1/4" beyond the mating nut (which is welded to the inside of the condenser housing). So, over the 13 years of service, the "naked" end of the screw was in the cooling fan air stream and apparently exposed to water that entered the area while the car was being driven, causing it to corrode. I was in a hurry and simply cleaned up the corrosion by running the screw through a die; but, you might want to consider changing the screw out to stainless......just in case you need to ever again change out the resistor. One of the posters had mentioned that the screw was corroded into place and he ended up rounding off the allen head socket.
As with the re-assembly of the oil cooler side of the car, assembly is simply "the reverse of the disassembly steps".
One last note. Upon inspection of the "inlet" side to the condenser, I was surprised to find a compacted build up of straw, leaves, and other debris impeding air flow through the condenser. It's hard to imagine how all that debris found its way through the opening in the bumper, but obviously it did. Be sure and inspect your condenser for such obstructions. I was able to easily vacuum out the debris after breaking it up with a screw driver (it was really packed in there). I also used compressed air to blow through from the other side of the condenser (the outlet side) to blow out any loose debris that might have been packed around the cooling fins.
That's the job. In total, I probably actually spent about 3 hours to do the work, of which a lot was spent just getting my tools ready and jacking the car up and putting it on jack stands. Removal and replacement of the bumper took about an hour. As you would guess, re-fitting the bumper took a while longer since it is a bit cumbersome (but not heavy) and I was careful setting it in place.
I also took extra time to clean up the areas exposed that were pretty dirty from never having been accessed in 13 years. So, in retrospect, I would say that the entire job is a simple DIY chore that can easily be accomplished in a half day by the average wrencher. I worked at a leisurely pace which included the consumption of some adult beverages and spent about 4 hours in my garage.
Certainly, abandoning the original resistors in place, and relocating the replacement resistors would have been much easier as has been noted by other folks. But, for me, there is something that likes to keep things "stock". Just the way I am wired, I guess.
Last edited by earossi; 08-06-2011 at 10:50 AM.
08-05-2011, 07:09 PM
#2
Instructor
Join Date: Sep 2005
Location: Greensboro, NC
Posts: 189
Likes: 0
Received 0 Likes
on
0 Posts
Thanks for the post; I have been on the same mission but unfortunately started with the A/C resistor and the DIY (either a post here, pcar.com or pcarworkshop.com) that said the replacement could be done without dropping the bumper and the condenser. It may be possible but I could not shrink my size XL hands down enough to get the resistor unscrewed from the back of the condenser. After much frustration I decided to go with Plan C last night and installed a replacement resistor on the inner fender well (DIY from pcar.com I think). I hope to get everything back together tonight or tomorrow depending on the weather.
08-05-2011, 08:18 PM
#3
Rennlist Member
Having convinced myself that the original ballast resistors controlling the fan low speed operation for both the oil cooler and A/C condenser were bad, I did a lot of research into the best way to replace them. The search function turned up a lot of posts on the topic, and most of them talked about what a PITA job it was to replace these parts. Then I ran into a posting that suggested removing the front bumper for access to both resistors.
My decision to remove the bumper was more to get into that area of the car for inspection and cleaning of the area. I guess it is a "curiosity thing" with me, just wanting to take things apart to see what is involved and to inspect things that you cannot without removing things.
Having taken that route, I am here to report that without a doubt.....removing the bumper is absolutely the easiest way to gain access to the resistors.
My decision to remove the bumper was more to get into that area of the car for inspection and cleaning of the area. I guess it is a "curiosity thing" with me, just wanting to take things apart to see what is involved and to inspect things that you cannot without removing things.
Having taken that route, I am here to report that without a doubt.....removing the bumper is absolutely the easiest way to gain access to the resistors.
for those that find removing the front BC too intimidating, you can leave it on and just remove the inner fender liners only.
check for a post from me ~ 5 weeks ago titled
"GT3Tek Headlight Squirter Delete install"
for some details.
PS, you'll need to remove the headlights to access a fastener that once removed greatly eases movement of the coolers.
Craig
08-05-2011, 10:34 PM
#5
Race Director
glad to hear that you are having good success.
for those that find removing the front BC too intimidating, you can leave it on and just remove the inner fender liners only.
check for a post from me ~ 5 weeks ago titled
"GT3Tek Headlight Squirter Delete install"
for some details.
PS, you'll need to remove the headlights to access a fastener that once removed greatly eases movement of the coolers.
Craig
for those that find removing the front BC too intimidating, you can leave it on and just remove the inner fender liners only.
check for a post from me ~ 5 weeks ago titled
"GT3Tek Headlight Squirter Delete install"
for some details.
PS, you'll need to remove the headlights to access a fastener that once removed greatly eases movement of the coolers.
Craig
08-06-2011, 09:19 AM
#7
Burning Brakes
Thread Starter
glad to hear that you are having good success.
for those that find removing the front BC too intimidating, you can leave it on and just remove the inner fender liners only.
check for a post from me ~ 5 weeks ago titled
"GT3Tek Headlight Squirter Delete install"
for some details.
PS, you'll need to remove the headlights to access a fastener that once removed greatly eases movement of the coolers.
Craig
for those that find removing the front BC too intimidating, you can leave it on and just remove the inner fender liners only.
check for a post from me ~ 5 weeks ago titled
"GT3Tek Headlight Squirter Delete install"
for some details.
PS, you'll need to remove the headlights to access a fastener that once removed greatly eases movement of the coolers.
Craig
Craig,
You have to remove the inner fender liners anyway using the DIY I mentioned in my post. Unfortunately, removing the inner fender liners ONLY does not allow for easy access to the bolts needed to drop the shelf that holds the oil cooler OR the condenser.
Trending Topics
08-06-2011, 10:30 AM
#8
Burning Brakes
Thread Starter
A/C Condenser Replacement - Success Part 2
OK. Finished the job and am posting doing the A/C condenser. I'll edit my first post; but, here is the rest of the story.
Actually, with removal of the A/C condenser attached to its "shelf" (exactly the same as for the oil cooler), changing the resistor out {which is bolted to the back side of the condenser housing) is much easier and faster than changing its sister resistor out on the oil cooler since there is no separate aluminum heat sink to remove, as was the case with the oil cooler.
With the condenser (attached to its shelf) broken loose from the inner fender, you can simply pull the shelf/condenser assembly out from the body of the car with one hand, while allowing it to hang on all its hoses, giving you unobstructed access with your other hand to the 4mm allen head cap screw that fastens the resistor to the back side of the condenser housing. So much access that I was able to use a 4mm allen head wrench at first to "break" the bolt loose (some minor corrosion had set in since the resistor was installed 13 years ago!). It was easy to get my entire hand in the area to use the wrench. Once I had broken the bolt loose, I switched to a 4mm allen head socket on a 3/8" drive socket wrench (would have been a little bit easier with a 1/4" drive, but my 3/8" gear was close at hand) which allowed me to quickly finish the unbolting operation.
Oddly, for my car anyway (a 1998 model), the oil cooler resistor was bolted to its heat sink with a hex head cap screw, while the A/C resistor was bolted to the housing with an allen head cap screw. The Germans never cease to amaze me! Being an engineer myself, I spend too much time trying to understand "why" they do the things they do!
The corrosion on the end of the cap screw that attached the resistor to the housing was due to its exposure to the atmosphere over the years. The cap screw is a bit long and the end of the screw protrudes about a 1/4" beyond the mating nut (which is welded to the inside of the condenser housing). So, over the 13 years of service, the "naked" end of the screw was in the cooling fan air stream and apparently exposed to water that entered the area while the car was being driven, causing it to corrode. I was in a hurry and simply cleaned up the corrosion by running the screw through a die; but, you might want to consider changing the screw out to stainless......just in case you need to ever again change out the resistor. One of the posters had mentioned that the screw was corroded into place and he ended up rounding off the allen head socket.
As with the re-assembly of the oil cooler side of the car, assembly is simply "the reverse of the disassembly steps".
One last note. Upon inspection of the "inlet" side to the condenser, I was surprised to find a compacted build up of straw, leaves, and other debris impeding air flow through the condenser. It's hard to imagine how all that debris found its way through the opening in the bumper, but obviously it did. Be sure and inspect your condenser for such obstructions. I was able to easily vacuum out the debris after breaking it up with a screw driver (it was really packed in there). I also used compressed air to blow through from the other side of the condenser (the outlet side) to blow out any loose debris that might have been packed around the cooling fins.
That's the job. In total, I probably actually spent about 3 hours to do the work, of which a lot was spent just getting my tools ready and jacking the car up and putting it on jack stands. Removal and replacement of the bumper took about an hour. As you would guess, re-fitting the bumper took a while longer since it is a bit cumbersome (but not heavy) and I was careful setting it in place.
I also took extra time to clean up the areas exposed that were pretty dirty from never having been accessed in 13 years. So, in retrospect, I would say that the entire job is a simple DIY chore that can easily be accomplished in a half day by the average wrencher. I worked at a leisurely pace which included the consumption of some adult beverages and spent about 4 hours in my garage.
Certainly, abandoning the original resistors in place, and relocating the replacement resistors would have been much easier as has been noted by other folks. But, for me, there is something that likes to keep things "stock". Just the way I am wired, I guess.
Actually, with removal of the A/C condenser attached to its "shelf" (exactly the same as for the oil cooler), changing the resistor out {which is bolted to the back side of the condenser housing) is much easier and faster than changing its sister resistor out on the oil cooler since there is no separate aluminum heat sink to remove, as was the case with the oil cooler.
With the condenser (attached to its shelf) broken loose from the inner fender, you can simply pull the shelf/condenser assembly out from the body of the car with one hand, while allowing it to hang on all its hoses, giving you unobstructed access with your other hand to the 4mm allen head cap screw that fastens the resistor to the back side of the condenser housing. So much access that I was able to use a 4mm allen head wrench at first to "break" the bolt loose (some minor corrosion had set in since the resistor was installed 13 years ago!). It was easy to get my entire hand in the area to use the wrench. Once I had broken the bolt loose, I switched to a 4mm allen head socket on a 3/8" drive socket wrench (would have been a little bit easier with a 1/4" drive, but my 3/8" gear was close at hand) which allowed me to quickly finish the unbolting operation.
Oddly, for my car anyway (a 1998 model), the oil cooler resistor was bolted to its heat sink with a hex head cap screw, while the A/C resistor was bolted to the housing with an allen head cap screw. The Germans never cease to amaze me! Being an engineer myself, I spend too much time trying to understand "why" they do the things they do!
The corrosion on the end of the cap screw that attached the resistor to the housing was due to its exposure to the atmosphere over the years. The cap screw is a bit long and the end of the screw protrudes about a 1/4" beyond the mating nut (which is welded to the inside of the condenser housing). So, over the 13 years of service, the "naked" end of the screw was in the cooling fan air stream and apparently exposed to water that entered the area while the car was being driven, causing it to corrode. I was in a hurry and simply cleaned up the corrosion by running the screw through a die; but, you might want to consider changing the screw out to stainless......just in case you need to ever again change out the resistor. One of the posters had mentioned that the screw was corroded into place and he ended up rounding off the allen head socket.
As with the re-assembly of the oil cooler side of the car, assembly is simply "the reverse of the disassembly steps".
One last note. Upon inspection of the "inlet" side to the condenser, I was surprised to find a compacted build up of straw, leaves, and other debris impeding air flow through the condenser. It's hard to imagine how all that debris found its way through the opening in the bumper, but obviously it did. Be sure and inspect your condenser for such obstructions. I was able to easily vacuum out the debris after breaking it up with a screw driver (it was really packed in there). I also used compressed air to blow through from the other side of the condenser (the outlet side) to blow out any loose debris that might have been packed around the cooling fins.
That's the job. In total, I probably actually spent about 3 hours to do the work, of which a lot was spent just getting my tools ready and jacking the car up and putting it on jack stands. Removal and replacement of the bumper took about an hour. As you would guess, re-fitting the bumper took a while longer since it is a bit cumbersome (but not heavy) and I was careful setting it in place.
I also took extra time to clean up the areas exposed that were pretty dirty from never having been accessed in 13 years. So, in retrospect, I would say that the entire job is a simple DIY chore that can easily be accomplished in a half day by the average wrencher. I worked at a leisurely pace which included the consumption of some adult beverages and spent about 4 hours in my garage.
Certainly, abandoning the original resistors in place, and relocating the replacement resistors would have been much easier as has been noted by other folks. But, for me, there is something that likes to keep things "stock". Just the way I am wired, I guess.
Last edited by earossi; 08-06-2011 at 10:51 AM.
